'97 Volvo Penta 5.7 GS PLKD Ignition Problem

[cmezzino]

Hello All, I am new to these forums. I have what I believe to be an ignition problem. Bought the boat, heads were blown as well as all the exhaust, etc. Rebuilt it all, got it running, pumping water, etc., but now, I believe I have an alternator that is overcharging, causing the ignition coil to "boil" Literally. Alternator is producing 15.3v at @1500 rpm and I get the same reading at the battery. Voltages are 12.6 with just the key on. This seems high to me. Exc. pole with purple wire at the alternator shows 14.4v and also 14.4v at the purple wire at the positive side of the coil with the engine running. When on the water, after about 15 minutes, engine simply will not achieve rpm and tach starts going crazy. It gets real sluggish. But every time I press the trim button to trim up or down, engine clears up just for second and sounds like it should. I am being told that the extra load on the system during the time I press the trim button is dropping the system's voltage down to the proper "range" which relaxes the voltage going to the coil in those moments, which is why the ignition "clears up" for that brief moment.

I have also confirmed this voltage drop with volt meter in the driveway with the same set of circumstances. I find a reference in the service manual that suggests that Alternator is over-charging, which is causing the coil to receive too much voltage and that an alternator output of over 14v is "overcharging." I replaced the voltage regulator on the back of the alternator and still have all of the same results and symptoms.

I'd like to confirm this, as a new alternator is a bit expensive and also that the ignition coil on this engine says "Use with external resistor" yet there is NO RESISTOR anywhere in the wiring, nor is there a resistor of any kind referenced in the service manual or wiring diagram. I believe the coil that is currently installed is the original coil from 1997 when the unit was new. It is a "Diamond E-035" which I see referenced in other forums.

I do not believe this to be a fuel delivery issue.

Fresh spark plugs are installed ACMR43T
Cap and rotor look fine.

I am a bit suspicious of the pick-up module inside the distributor as well.

Any information, advice instructions, etc. are most appreciated. Surely someone out there has experienced this or something similar.

 

[79_banshee]

I thought that the resistor was part of the regulator on the alt but I could be wrong.

 

[cmezzino]

I hadn't considered that but that's interesting. I'll check that out. I have a new alternator on the way and I'm curious to see if that makes a difference as well. Alternator needs to be replaced either way as the bearing in it has become really noisy.

 

[bruceb58]

Your alternator is bad. Whether it is the cause of your ignition issue, you will soon find out. There is no resistor anywhere.

 

[cmezzino]

Thank you, Bruce. New alternator arrives tomorrow. Can we confirm that the correct ignition coil is 12v to be used with an external resistor, even though there is no resistor? This is what the replacement part would suggest.

 

[bruceb58]

You have electronic ignition. Therfor6, no resistor at all.

 

[cmezzino]

Ok, new alternator arrived today. Sierra 18-6261. Put it on and still ALL the same readings. 15.3v charging and at battery and 14.3 at the positive side of the coil. I'm truly puzzled at why such a high voltage both from brand new alternator and coil. Is there ANYTHING else I should be checking that might explain why I am getting too much voltage? I even tried a different battery and still all the same. I checked for resistance in both battery cables and all alternator wires and there is no resistance in any of those wires. Again, truly puzzled.

 

[mikeneal]

That is super strange the new alt has same over charge issue. Is it possible your voltage meter is whacky? Maybe take old alt to local autoparts the big box ones typically will test starters, batteries and alternator for free.

 

[cmezzino]

Yeah Mike I've been using a volt meter as it's hard to tell the accuracy of the gauge on the dash. I had the old alternator bench tested at an alternator repair shop because all the auto parts stores said they could not test a marine alternator because there is no wiring harness connection. I have a new theory on what may be the problem but I'm gonna hold off on the reveal until I confirm.

 

[bruceb58]

Where is the sense terminal of the alternator wired up to? Wire it straight to the alternator output.

 

[gbeltran]

I'd check the wires and connections. Grounds good? As Bruce asked where is the sense wire located? If it's got a crappy connection the alternator will increase the output until it sees (senses) the specified voltage at that wire.

 

[cmezzino]

Using the procedure in the service manual, we tested the pick-up module inside the distributor and it tested bad. So we replaced it. (Pertronix IG-1589). We literally traced every wire in the entire system looking for a short, bad ground, anything that might explain why still over 15 volts. Although the battery was only about 6 weeks old, I took it and had it checked and it tested bad because of a lack of CCA, which was weird because I never did have trouble with it starting. But anyway, they replaced for free, so I took it. Replaced into the boat and all the voltages dropped about .3v, but still too high.

Bruce stated that there needs to be a jumper wire that connects the sense terminal to the B+ output on the alternator. That jumper wire was not present on the original alternator (3856600) and it is not present in the wiring diagram for my year model (1997). What IS jumpered is the purple EXC wire across and over to the sense post. I go back to the wiring diagrams and find that year model 2000 shows the jumper between the sense terminal and B+ just like Bruce said. All voltages came down into the acceptable range, but engine would not turn off, even by disconnecting the battery. Went back to the wiring diagram and noticed the diagram ELIMINATES the jumper EXC and SENSE. Tried it. FIXED! I guess with the jumper between EXC and SENSE and B+ those jumpers effectively bypassed the ON side of the ignition switch.

Voltage at B+ and battery with engine running is now 14.45. Positive side of the coil reads about 13 and about 7.3 on the negative side of the coil. This is much more in line with what I believe I should see. Engine running very smooth and quiet. NOTE: Timing has to be reset after installing the Pertronix IG-1589 because the sensor inside is in a little different spot.

If anyone sees any issues with what I've done here, please let me know. The real test will be out on the water.

 

[bruceb58]

You never want to have a connection between the excite and B+. Normally, you would only have a jumper between excite and sense but the problem is if there was a huge voltage drop from the battery back to your console through your ignition switch and then back to the alternator, you could have to much voltage at the output of the alternator.

I wanted you to add that wire as more of a test although there is no problem on doing it that way as long as it doesn't energize the excite.

 

[cmezzino]

Bruce, it did not appear to energize the excite so long as I had removed the smaller jumper between excite and sense. I took the boat out yesterday for a test run and it ran and performed beautifully! Not a single problem. I bought the boat in very poor condition because I saw the potential, but man this has been a pretty intense project. I've been working on it about 2 months now. I sure have learned a lot of valuable things in this process.

I'm going to start a new thread question regarding an engine idle question.

Thank you all!